Adventurers are part of the ecosystem. They eat (see, for instance, my prior post on cooking what they eat) and are eaten (see, for instance, a hungry dragon). But do they feel like they impact the ecosystem?

In reality, a single party of adventurers are unlikely to drastically alter the ecosystem unless they are taking foraging in the wilderness or hunting in the dungeon to the extreme. But, similarly, a band of misfits are also unlikely to alter the dynamics between powerful factions. Best practice is to err slightly less hard in the direction of realism (which, in games, is primarily a useful guide to the extent it promotes agency) and towards increased impact for player action, thereby making the choices they make, whether to hunt or to overhunt, matter more. 

Initially, I was going to have the referee track every time the party hunts in a region or how many of a creature type have been killed. These are still a valid way of accomplishing my goal (and is used in this post at the Hill Cantons about dynamic sandboxes) but a tad fiddly for my tastes. When I’m running a game, unless counting the numbers of goblins massacred thus far is central to the campaign, I’d like to skip as much direct bookkeeping as possible. 

There are numerous ways to structure a random encounter table. In a post earlier this year, I posited a method for a fairly structured encounter table system that would devise multiple aspects, such as surprise and number appearing, from a single toss of the dice. For the ecological purposes of this post, however, we must employ another method. 

Create a random encounter table that reflects the ecosystem of the region or dungeon. The more populous, well-established or well-adapted a specific encounter type is, the lower their position on the table. More rare creatures, especially endangered creatures, place higher, with the last result typically being a singular creature, the only one of its kind in an area. I am assuming a 2d6 encounter table, but we are less concerned here with any specific statistical formulation rather than the general idea. 

After players kill a creature in the adventure site that is listed on the random encounter table (even if not encountered randomly), roll 1d12 (for a 2d6 table, but if your table is 2d4, roll 1d8; if 3d6, roll 1d20, etc., season to taste). If the result is below the creature’s place on the table, they have killed the last of that type of creature in the area, other than any that remain in a keyed area of the area. Remove their result and replace it (I provide some guidance for this below). If the result is above the creature’s position, there is no appreciable change in the creature’s prevalence. If the die result matches exactly the encounter’s position, creatures of that type begin some type of defensive measures against extinction—perhaps they become immediately hostile to the player-characters and other adventurers, perhaps they seek out reinforcements, or perhaps they begin actively hunting the party in response. For any creature that was singular in the dungeon, it is replaced by a similarly deadly predator, looking to fill the now-empty niche. There is always a bigger fish. 

For each result on your encounter table, determine if it is more predator or prey. Typically prey are lower (as a number, but not in top-to-bottom positioning…the way tables are structured make it difficult to say “lower”) on the table and predators are higher, but that may not always hold true. 

When prey is eliminated as a result of the above-described method, move another creature on the table that preyed upon it most often higher in the table by one, swapping it with whatever was in its place. Move any other prey creatures that it competed with for resources and were above it on the table to be lower in the table by one. In the resulting empty space, put a new prey that fills a similar ecological niche as the one that was just removed. 

When a predator is eliminated as a result of this method, move another predator on the table that it competed for resources with most often lower by one, swapping it with whatever was in its place. Move any creatures it preyed upon and that were higher than it in the table, if any, to be lower by one. In the resulting empty space, put a new predator that desires the same resources previously consumed by the one that was just removed. 

This can be relatively simple in practice and can be done between sessions as part of your ordinary restocking procedures. Take, for instance, the below random encounter table. 

Let’s say that, using the above table, the party encounters a few gray wolves and kills them. After killing the wolves, the referee rolls 1d12 which comes up as a 4, indicating that these were the last of their kind in the area. So the referee removes that result from the table. Because gray wolves are predators, the referee will move the wolverines, which likely competed with the gray wolves for resources lower by one, swapping it with the wood bison. The mountain elk are prey that the gray wolves may have hunted that are also higher than the wolves in the results, so the referee will move it to be lower by one to the space previously occupied by the gray wolves. The absence of the gray wolves causes a new species of carnivore to enter the area, so the referee will fill in the empty space with mountain lions coming from the neighboring region. Simple as.

As a reminder, the Barkeep Jam is LIVE and running until August 14! So go forth and make your own pub and pub accessories for the pubcrawl pointcrawl, or just go and check out what has been made so far. The first submission, Buried Base of the Boozed Barrel Burglars, is a small dungeon crawl that you can insert into nearly any of the pubs in the base adventure. An excellent dungeony reprieve from a largely social adventure.

Also, the my friend Anne’s LEGO RPG Setting Jam is still running for the next few weeks. Check out my own submission, Trouble in Paradisa, a Lego murder mystery, which is on DriveThruRPG and Itch (PWYW on both, but due to the vagaries of Itch, it is free there via the 2,000 community copies I included).